Breast cancer is a major health problem affecting millions of women worldwide. One of the ways to combat breast cancer is by early diagnosis and administration of effective therapy. For those patients whose disease is diagnosed at a late stage, accurate monitoring for assessing response to treatment is important. Unfortunately, until now, there is no effective means for diagnosing breast cancer or for monitoring, due to the lack of high-quality blood-based biomarkers. In this grant application, our aim is to validate two newly discovered candidate breast cancer biomarkers. We will use samples that have been collected before treatment [for the diagnostic application] and samples that have been collected during therapy, over many years [for the application of monitoring response to therapy]. Our preliminary data indicate that these newly discovered biomarkers perform better than the classical and commercially available breast cancer biomarker, CA15.3. If our results are promising, they may lead to new ways for early diagnosis of breast cancer and for better monitoring of those patients who are treated with chemotherapy or other regimens. Our positive data may improve the way breast cancer is diagnosed and monitored, with the ultimate goal of extending patient survival and improve quality of life. PUBLIC HEALTH RELEVANCE: We have recently discovered two new breast cancer biomarkers. Our preliminary data are highly promising, regarding use of these biomarkers for early diagnosis of breast cancer and for monitoring patients who have advanced disease and are treated with various modalities. If we are successful, these two new novel biomarkers may play a major role in improving the diagnosis of early breast cancer and in optimizing therapeutic regimens of patients who already have the disease.